This invention relates to a method for applying a puncture sealant to tire components mounted upon a tire building drum, and to a tire having such a built-in sealant.

• "Axial" and "axially" means the lines or directions that are parallel to the axis of rotation of the tire.
• "Inner Liner" means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
• "Radial" and "radially" mean directions radially toward or away from the axis of rotation of the tire.

The invention relates to a method according to claim 1 and to a tire according to claim 9.

Dependent claims cover preferred embodiments of the invention.

The structure, operation, and advantage of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings wherein:

• Figure 1 is a schematic view of a cross section of a tire with a sealant;
• Figure 2 is a schematic view of a cross section of the sealant, barrier and innerliner layers;
• Figure 3 is a schematic view of a cross section of the sealant, barrier and innerliner layers in an alternative embodiment.

Referring now to Figures 1, 2 and 3, there is illustrated a cross-sectional view of a self-sealing pneumatic tire constructed in accordance with the invention. The tire 2 includes sidewalls 3, a supporting tire carcass 4, a pair of beads 5, an inner liner 6, a sealant layer 7, a barrier layer 9 and an outer circumferential tread 8. The sidewalls 3 extend radially inward from the axial outer edges of the tread portion 8 to join the respective beads. The carcass 4 acts as a support structure for the tread and sidewalls, and is comprised of one or more layers of ply. Sealant layer 7 is shown disposed between the inner liner 6 and a barrier layer 9. The sealant layer 7 may also be disposed at different locations as described in more detail below. The tread region 8 forms a crown region of the carcass. In the interior region of the tread, there is generally found one or more belts. The surface region of the tread forms a tread pattern.

The sealant layer 7 may comprise polymer compositions such as described in US-B- 4,895,610. The polymer compositions described therein include the following composition by weight: 100 parts of a butyl rubber copolymer, 10 to 40 parts of carbon black, 5 to 35 parts of polyisobutylene, 5 to 35 parts of an oil extender, 0 to 1 part of sulfur, and from 1 to 8 parts of a peroxide vulcanizing agent. A second polymer composition includes the following composition by weight: 100 parts of a butyl rubber copolymer, 20 to 30 parts of carbon black, 8 to 12 parts of polyisobutylene, 8 to 12 parts of an oil extender, 0.1 to 0.4 part of sulfur, and from 2 to 4 parts of a peroxide vulcanizing agent.

The sealant layer 7 may also comprise a colored polymer composition such as described in US pending patent application No. 10/917,620 filed on August 13, 2004. The colored polymer composition may comprise, based upon parts by weight per 100 parts by weight of said partially depolymerized butyl rubber exclusive of carbon black:

• (A) a partially organoperoxide-depolymerized butyl rubber as a copolymer of isobutylene and isoprene, wherein said butyl rubber, prior to such depolymerization, is comprises 0.5 to 5, preferably within a range of from 0.5 to 1, percent units derived from isoprene, and correspondingly from 95 to 99.5, preferably within a range of from 99 to 99.5, weight percent units derived from isobutylene;
• (B) a particulate reinforcing filler comprising:
  1. (1) 20 to 50 phr of synthetic amorphous silica, preferably precipitated silica, or
  2. (2) 15 to 30 phr synthetic amorphous silica, preferably precipitated silica, and 5 to 20 phr of clay, preferably kaolin clay, or
  3. (3) 15 to 30 phr synthetic amorphous silica, preferably precipitated silica, and 5 to 20 phr of calcium carbonate,
  4. (4) 15 to 30 phr synthetic amorphous silica, preferably precipitated silica, 5 to 15 phr of clay, preferably kaolin clay, and 5 to 15 phr of calcium carbonate;
• (C) from zero to 6, alternately 0.5 to 5, phr of short organic fibers
• (D) a colorant of other than a black color wherein said colorant is selected from at least one of organic pigments, inorganic pigments and dyes, preferably from organic pigments and inorganic pigments;
• (E) from zero to 20, alternately 2 to 15, phr of rubber processing oil, preferably a rubber processing oil having a maximum aromatic content of 15 weight percent, and preferably a naphthenic content in a range of from 35 to 45 weight percent and preferably a paraffinic content in a range of 45 to 55 weight percent.

Other sealant polymer compositions which may be utilized by the invention are described in US-B-6,837,287.

Further, a sealant polymer composition may also be used with the invention that has a polymer composition of butyl rubber and an organoperoxide vulcanizing agent which becomes activated at high temperatures above 100°.

A first embodiment of manufacturing a tire is described as follows. The sealant polymer composition is mixed using a banbury mixer, at an optional remote location from the tire building plant or at the tire building plant. After the polymer composition is mixed, the polymer composition is then milled and formed into sheets of the material, wherein the sheets are separated from each other by silicone coated liners. One example of a silicone coated liner which will separate from the polymer composition is a silicone coated woven fiberglass cloth (coated on both sides of the liner) made by Precision Coating Co., Inc., of Dedham, MA and sold under the trade name S/W 10. Another example of a liner which would separate from the polymer composition is a siloxane coated nylon cloth made by Highland Industries.

Next, the sheets of the sealant polymer composition are separated from the liner and fed into one or more mills or heated calender rolls which break down the compound and soften it up by heating. One or more of the mills may be optionally corrugated. The rolls are preferably heated to a temperature sufficient to prevent sticking of the sealant to the rolls. The one or more mills output a continuous strip of sealant polymer composition 15.8 cm to 20.3 cm wide.

Next the continuous strip of sealant polymer composition is fed strip into a hot feed screw type extruder wherein the sealant polymer composition is heated to 93°C to 105°C, more preferably in the range of 101°C to 103°C. The extruder has a die to form the sealant polymer composition into its final shape, which is shown in Figure 2. The final shape of the sealant has a cross-sectional shape that has an upper and lower surface that are approximately parallel, with angled or tapered sidewalls. The angle of the tapered edges range from 15 to 30 degrees. The uncured width of the sealant is 15.8 cm to 22.9 cm or a width sufficient to extend from shoulder to shoulder of the tire. The uncured thickness of the sealant is 0.64 cm, although the range of the thickness and width can very depending upon the application. The uncured thickness may range from 0.125 cm to 1.90 cm. For example, if the sealant is used in a passenger tire, an uncured thickness of 0.32 cm may be desired, while for a truck tire an uncured thickness of 0.64 cm in may be desired.

A cold feed extruder may also be utilized, eliminating the need for preheating of the sealant polymer composition. The internal temperature controls of the cold feed extruder may be utilized to heat the composition in the range of 93°C to 105°C, more preferably in the range of 101°C to 103°C.

The output of the extruder is fed onto a conveyor belt. The extruded sealant polymer composition may then be optionally sprayed with water or cooled gas to cool the sealant polymer composition to below 38°C.

The extruded sealant may then be cut to length with a heated knife or ultrasonic knife and then the composition may be stored in steel tray storage trucks or bear traps.

During the entire processing of the sealant prior to vulcanization, it is preferred that the temperature of the sealant be below the peroxide activation temperature.

In a second embodiment of the invention, a gear pump extruder may be utilized, eliminating the need for preheating of the sealant polymer composition. Varying the extruder speed can independently control the temperature of the sealant composition. Further, the gear pump is a constant volume device, which will allow application of the sealant composition directly onto the tire building drum. An advantage to the gear pump extruder allows the starting and stopping of the output extrudate without wasting material.

A third embodiment of a manufacturing process for making a tire with a sealant layer is described as follows. First the polymer composition selected for use in the sealant layer 7 is mixed in a banbury mixer. The polymer composition is then fed to an extruder, either a hot feed extruder or a cold feed extruder. The extruder has a screw feed mechanism and a die. The die is shaped to form a cross-sectional shape of the extruded sealant as shown in Figure 2. The cross-sectional shape of the sealant is approximately an elongated rectangle with angled or beveled outer edges. The strip output from the extruder has a width in the range of 15.8 to 20.3 cm. The strip is extruded onto a spacer fabric which has spacers on the side of the fabric to ensure that the composition does not get deformed when rolled up and stored on a spool. The spool can then be transported to the tire building drum where the sealant component is cut to the desired length and mounted to the tire.

The sealant layer in all of the above embodiments may be positioned between the innerliner and barrier layer or between the innerliner and carcass. It is preferred that the sealant layer be completely encased or encapsulated between the rubber layers to prevent migration of the sealant. The built-in sealant layer may, for example, be positioned between a tire innerliner rubber layer and tire carcass or between two tire innerliner rubber layers wherein said sealant layer may:

• (A) extend from one shoulder of the tire to the other through the crown region of the tire;
• (B) be positioned in at least one tire shoulder area region and extend into at least a portion of the adjoining tire sidewall portion of the tire, or
• (C) extend from sidewall-to-sidewall through the tire crown region.

When the sealant layer is positioned between a first rubber layer and a second rubber layer, it is preferred that the sealant splice be located at a different location than the splice of the first and second layers. It is also preferred that the sealant splice be stitched before the second rubber layer is added thereon.

The thickness of the sealant composition layer can vary greatly in an unvulcanized puncture sealant-containing tire. Generally, the thickness of the sealant composition layer may range from 0.13 cm to 1.9 cm. In passenger tires it is normally desired for the sealant composition layer to have a thickness of 0.32 cm (0.125 inches) whereas for truck tires, a thickness of 0.76 cm (0.25 inches) or greater might be desired.

After the unvulcanized pneumatic rubber tires of this invention are assembled they are vulcanized using a normal tire cure cycle. The tires of this invention can be cured over a wide temperature range. For example, passenger tires might be cured at a temperature ranging from 130°C to 170°C and truck tires might be cured at a temperature ranging from 130°C to 170°C. Thus, a cure temperature may range, for example, from 130°C to 170°C and for a period of time (e.g. from 10 to 45 minutes or more depending somewhat upon the size of the tire and the degree of desired depolymerization of the butyl rubber as well as the thickness of the sealant layer itself) and sufficient to at least partially depolymerize said sealant precursor layer to the aforesaid storage modulus (G') physical property. In practice, a period of time used to vulcanize the tires, in a suitable mold, may therefore, for example, have a duration of 10 to 14 minutes for a passenger tire and for 25 to 55 minutes for a truck tire.

Whereas the embodiment shown in Fig. 2 has a sealant layer 7 placed on the inner liner 6 and covered or enclosed by the barrier layer 9 (or alternatively by the carcass 4 (not shown in Fig. 2)), Fig. 3 shows an embodiment of the invention where the sealant layer 7 is divided into a plurality of cells 11. These cells 11 are preferably arranged substantially in parallel adjacent to each other. Preferably, the cells are separated from each other by at least one partition wall 10 having a thickness in a range of from 0.3 mm to 4 mm for instance. The example of Fig. 3 shows six adjacent cells filled by the sealant and separated from each other by five partition walls 10. The partition walls may be made of the material of the barrier layer 9, of the material of the innerliner 6, of an other rubber material, of a silicone coated liner or of a siloxane coated nylon cloth for instance. The number of cells 11 is largely a matter of choice and can for instance vary from 2 to 10, alternatively from 3 to 7. The width of the cells 11 shown in Fig. 3 is preferably in the range of 1.5 to 12 cm. More preferably, the width is 2 to 4 cm. It should also be emphasized that the width of the cells needs not to be the same and that the cells can be arranged in a symmetrical (as shown in Fig. 3) or an asymmetrical way with regard to the equatorial plane of the tire 2. The cells 11 may also have tapered sidewalls. One method to create the plurality of cells 11 made or filled with sealent is mounting the inner liner 6 onto a tire building drum, extruding the sealant composition into at least one strip substantially having the width of the cell 11 to be created, hellically winding the stip over the inner liner 6, and layering the barrier layer 9 (or alternatively the carcass 4 over the at least one strip mounted over the inner liner. The partition walls 10 are preferably applied as a sidewall on at least one side of the strip before winding it over the inner liner 6. They may also be extruded together with the sealant composition and applied as thin rubber layer on one or both sidewalls of the extruded sealant strip.